How come Super Sentai doesn't have a fictional city like Zawame city from KRG
 

For Example in Kamen Rider W, The city was Futo City while Kamen Rider Gaim take place in Zawame City. Why Super Sentai hasn't made a fictional city?

They have...I believe Go-Busters' city was fictional.

Yep. That's right as SideswipePrime says, in that Go-Busters had the signature city.

I think maybe why it's not as regular in Sentai as Rider though, is that it's more powerful thematically when a single hero takes it upon himself alone to nobly defend a city. When a team decides to do so, the impact is lessened a bit.

It's like how a lot of Riders are semi-tragic heroes because they have to take a huge burden on themselves, while Sentai teams have each other to form a strong whole/sum of parts. So while Haruto in Wizard, for instance, had to be the sole "final hope", this wouldn't be necessarily as powerful a statement if a team of good friends had to fill that role.

So, I guess, along those lines, having a team defend a city might feel more like any Police/local law enforcement/military organisation (which some Sentais have been, to be fair) and being part of some unit that's designed to protect a place is sooort of less striking than one hero that's lost it all, still deciding to do the right thing. Like Shotaro in W losing his parents and his mentor, but still loving the city.

But still a Sentai could do it, I mean the Power Rangers have had plenty of fictional cities. Though I do like when they protect multiple places around the World.

They could, I mean Go-Busters has as previous posts mentioned. But some series just focus more on characters than setting. Since Rider pretty much uses everything around it, it make more sense depending on the show. Heck, every Power Ranger series pretty much has its own fictional city, it just depends on that season I guess.

I just go ahead and assume that it's because they want people to believe that it could happen anywhere, but I really have no idea.

Cities in Tokus are mostly not mentioned by name, except for those that are important to the plot. So basically, we usually don't even know whether the city is fictional or not. As long as it is not stated in the show, it could be both a fictional or a real city.
As for some shows, we do know they take place in Tokyo, namely Kabuto and Go-Busters, because the Tokyo Tower is important in both of them- so Go-Busters is NOT set in a fictional city, as the title of the summer movie proves.

Besides, fictional cities are by far not as often used as you guys make it sound like. Futo and Zawame, which both have a special relation to the plot, are the only noteable examples that come to my mind.

I thought it was called the Enetron Tower in Go-Busters...

The movie is called "Protect the Tokyo Enetower"

Oh...ok. I never watched to movie. :lol